Fertilizer manufacture



Patented Mar. 15,1932

UNITED STATES PATENT? HANS SVAN OE, 0]! WILMINGTON, DELAWARE,

POBATION' OF DELAWARE I FERTILIZER MANUFACTURE Io Drawing.

This invention relates to fertilizers, particularly to phosphate fertllizers'contaimng nitrogen and methods for the manufacture thereof.

fate is avoided. Both of these factorsv are advantageous in that a more concentrated fertilizer is produced. Generally speaklng,

however, nitrated superphosphate, the reac-' tion product of phosphate rock and nitric acid, leaves much to be desired because of the presence of 1 calcium nitrate therein, which, being hygroscopic,--makes the drying of nitrated superphosphate as well as its preservation in a dry state quite difficult.

With a view to avoiding these and other disadvantages characteristic of previously known fertilizers of the type referred to, it

is the object of the present invention to produce a concentrated fertilizer high in available phosphorus and nitrogen.

It is a further object of the invention to provide anew and improved process for producing a fertilizer of the character described.

Other objects and advantages of the invention will be apparent as it is better understood by reference to the following specification in which its details and preferred em-- bodiments are described,

In accordance with the resent invention I roduce a concentrated ertilizer by reacting phosphate rock, for. example Florida phosphate, coprolite, apatite, etc, with nitric acid and ammonium carbamate. This is ac complished by decomposing the phosphate rock with nitric acid and treating the resultant product with ammonium carbamate to produce a fertilizer which isnot only high in nitrogen and available phosphorus but also 60 relatively stable, non-hygroscopic and non- Application filed September as, 1929. Serial No. saaaoo.

corrosive and otherwise well adapted to the Y ratuirements of storage, shipment, and dis-' tri ution. Various proportions of nitric acid may be used in effecting the decomposition of phosphate rock, depending largely upon the desired chemical content of the final product. Thus I may use nitric acid of suchamount and concentration as to convert substantially all of the tricalcium phosphate in the rock to monocalcium (water soluble) phosphate with which there i 68% tricalcium will be associated .calcium nitrate and some free ,acid; For instance,'this may be accomplished with a rock containing. phosphate by using about assIenon, -nx mns m Manama mo f n. I. no 201w 1m nmouns a comm, or WILMINGTON, nnmwana, a cenof rock. However, I have found that it is not necessary for the purpose of the present invention to decompose thez roc'k completely to monocalcium (water soluble) phosphate, as

a final product containing satisfactorilyilow proportions Ofcitrateinsoluble P 0, may be obtained by using in the decomposition stage proportions of nitric acid as low as 80% of those above stated. Generally speakin it is desirable for the satisfactory accomplishment of the objects ofthe invention that such amounts of nitric acid be used as will correspond .to from about 3-5 moles of HNO,- per mole of P 0, in the phosphate rock, plus .the amount of acid chemically equivalent to the non-phosphatic constituents (calcium carbonate, calcium'fluoride, etc.) of the rock. With less than the 'quantityof HNO, indicated I have found that not all of the tricalcium phosphate is reacted upon; with acid'is wasted, principally by more, nitric volatilization due to heat of reaction. :21

While the invention is not limited fljto the use of any particular temperature in the addition of ammonium carbamate, I have observed that a temperature below 40 0., the

calcium nitrate in the phosphate rock-nitric I acid decomposition product tends to crystallize with the result that the mass becomes hard and diflicultly workable. In my process, therefore, I prefer to mix ammonium carbamate with the still warm decomposition prod not of phosphate rock and nitric ,acid, thus ]utilizing the heat of the decomposition to preserve the mass in a more or less fluid condition favorable to the more satisfactory incorporation of ammonium carboa mate therewith. Whether the decompositi 11 product is pasty, mushy or practica ly'liquid will depend not only upon its temperature but also upon the concentration and quantity of nitric acid used in opening up the rock.

The proportions .of ammonium oarbamate used to react with the decomposed rock may be varied within relatively wide limits depending upon the desired physical form and chemical content of the fina product. For example, suflicient ammonium carbamate may be mixed with the nitrated superphosphate to neutralize the free acidand to react with a part or all of the calcium nitrate present; or the reaction may be made to go still further by adding enough ammonium carbamate to convert substantially ll of the phosphoric 1 acid, present as mono-, di-ontricalcium phosphates, to monoor diammonium phosphates.

By decomposing phosphate rock with ni tric acid and treating the resultant'product with sufficient ammonium carbamate to neutralize the free acid and to react with sub: stantially one-half of the calcium nitrate present, a stable phosphate fertilizer, containing both ammonium nitrate and calcium nitrate, may be obtained. The non-hygroscopic and stable character of this product is the more surprising on account of the known avidit of calcium mtrate and ammonium nitrate or water.

Moreover, if desired, a product containing.

even higher proportions of nitrogen may be obtained by decomposing phosphate rock calcium carbonate,

all of the calcium nitrate present.

with nitric acid and mixing with the resultant product sufiicient ammonium carbamate to neutralize the free acid and to react with For example, by decomposing 68% Florida phosphate rock with 50% nitric acid and thereafter 'mixing the product with suificient ammonium carbamate to neutralize free acids and to react with all of the calcium nitrate present, a very desirable fertilizer containing dicalcium phosphate and ammonium nitrate in approximate molar ratios of 1:1.3:3.6 may be produced. Calcium carbonate, although to some extent an inert material in fertilizers, is of demonstrated high value in eliminating soil acidity. Ammonium nitrate is particularly desirable because of its high nitrogen. content.

By efiecting the decom osition of phosphate rock with nitric aci and treating the decomposition product with even higher pro-' ortions of ammonium carbamate, a fertiizer may be produced, containing, besides ammonium nitrate and calcium carbonate, monoor diammonium phosphates or mixtures thereof with only a relatively small proportion of citrate insoluble P 0 This type of fertilizer is particularly advanta- 1660 parts by weight of acid to 1000 parts by weight of rock. With 200 parts by Weight of the resultant product while warm (above 40 C.) there was mixed 15.7 parts by weight of substantially pure ammonium carbamate, which is approximately quired to convert the calcium nitrate in the decomposed rock. After cooling, the product analyzed 13.2% total phosphoric acid (calculated as P 0 of which 34.2% was water soluble, 64% citrate soluble, and 1.8% citrate insoluble phosphate. The per cent. by weight of citrate insoluble P 0 based on the total weight of the product was 0.24%.

Example .Z.-Two hundred parts by weight of a warm decomposition product similar to that used in Example 1 was treated with 38.7 parts of ammonium carbamate, which is somewhat in excess of that required to react with all the calcium nitrate in the decomone-h'alf that reposed rock. The resultant fertilizer analyzed 11.65% total P 0 of which 97.4% was citrate soluble and 2.6% citrate insoluble phosphate. In this case, all of the monocalcium phosphate was apparently converted to dicalcium phosphate. The product contained 5.8% ammonia nitrogen and 6.4% nitrate nitrogen or a total of 12.2% nitrogen. The per cent. of citrate insoluble P 0 based upon the total weight of the resultant product was 0.30%. It will be noted that, although twice as much ammonium carbamate was used in this case as in the previous example, there was no substantial increase in reversion to citrate insoluble phosphate.

, Proportions of ammonium carbamate in considerable excess of those in the above examples may nitrogencontent of the final product without causing appreciable reversion to citrate insoluble P 0 For example, by reacting 200 parts of a phosphate rock-nitric acid decom* position product, similar'to that used in the foregoing examples, with 75 parts of ammonium carbamate, the total nitrogen was increased to about 14.5% with a totalcitrate insoluble P 0 in the resultant product of only 0.17%.

The products prepared in accordance with theforegoing examples may, if desired, be

used directly in the preparation ofso-called be used in order to increase the highest grade fertilizer materials, or they may advantageously be used alone, in which case before packing and shipment they are preferably submitted to drying in the known manner.

Generally speaking, the ammonium carbamate used in the process should be of the procurable and economically feasible to use. Avoidance of the presence of the ammonium carbonates is recommended, although not essential, as I have found that these salts are in no sense the equivalent of the carbamate, particularly as regards the degree of reversion to citrate insoluble phos-'' trated fertilizer containing available phos phorus and nitrogen which, comprises reacting phosphate rock with nitric acid and treatmg the resultant product with suflicient amposing phosp monium carbamate to render the fertilizer substantially non-hygroscopic.

2. The process of manufacturing a concentrated fertilizer containing available phosphorus and nitrogen which comprisesv reacting phosphate rock with nitric acid and treating the resultant product in a warm condition with sufiicient ammonium carbamate to render the fertilizer substantially non-hygroscopic.

3. The process of manufacturing a concen trated fertilizer containing available phosphorus and nitrogen which comprises reacting phosphate rock with nitric acid and treating the resultant product at a temperature in excess of about 40 C. with sufficient ammonium carbamate to render the fertilizer substantially non-hygroscopic.

4. The process of manufacturing a concentrated fertilizer containing available phosphorus and nitrogen which comprises decom posing phosphate rock with suitable proportions of nitric acid to convert substantially all of the tricalcium phosphate contained therein to water soluble calcium phosphate and reacting the resultant product with sufiicient ammonium carbamate to render the fertilizer substantially non-hygroscopic.

5. The process of manufacturing a concentrated fertilizer containing. available phosphorus and nitrogen which comprises decomhate rock with suitable roportions of. nitric acid to convert substantially all of the tricalcium phosphate contained therein therein to water soluble to water soluble calcium phosphate and reacting the resultant product in a warm condi-,

tion with sufiicient ammonium carbamate to render the fertilizer substantially non-hygroscopic.

6. The process-of manufacturing a concentrated fertilizer containing available phosphorus and nitrogen which comprises decomposing phosphate rock with suitable proportions of nitric acid to convert substantially all of the tricalcium phosphate contained calcium phosphate and reacting the resultant product at a tern: perature in excess of about 40 C. with sufficient ammonium carbamate to render the fertilizer substantially non-hygroscopic;

7. The process of manufacturing a concentrated fertilizer containing available phosphorus and nitrogen which comprises reactmg phosphate rock with nitric acid to yield a product containing free acid and calcium nitrate, and treating the same with proportions of ammonium carbamate sufficient to neutralize the free acid and to react with at least a part of the calcium nitrate.

8. The process of manufacturing a concentrated fertilizer containing available phosphorus and nitrogen which comprises react- .mg phosphate rock with nitric acid to yield a product containing'free acid and calcium nitrate, and treating the same in a warm condition with proportions of ammonium carbamate suflicient to neutralize the free acid and to react with at least a part of the calcium nitrate.

9. The process of manufacturing a concentrated fertilizer containing available phosphorus and nitrogen which comprises reacting phosphate rock with nitric acid to yield a product containing free acid and calcium nitrate, and treating the same at a. temperature in excess of about 40 C. with proportions of ammonium carbamate sufficient to neutralize the free acid and to react with at least a part of the calcium nitrate.

10. a The process of manufacturing a concentrated fertilizer containing available phosphorus and nitrogen which comprises reacting phosphate 'rock with nitric acid to yield a product containing free acid and calcium nitrate, and treating the same with proportions of ammonium carbamate suflicient to neutralize the free acid and to react with substantially all of the calcium nitrate.

In testimony whereof, I alfix my si ature.

. HANS SVA OE. 

